Extrusion is a phenomenon in sealing technology that affects the life of a seal, especially in dynamic applications. In particular, the sealing part of the seal assembly, such as the elastic seal lip, can be extruded during service due to the high pressure application that the seal attempts to seal against. The higher the media pressure, shaft speed and temperature, the more critical the extrusion becomes, and thus the more important it is to minimize the extrusion gap, that is, the clearance that exists between the shaft and the supporting means receiving the seal body. There are applications wherein such supporting means is a sidewall of the cavity receiving the seal body. In other applications, particularly in demanding dynamic applications, the supporting means essentially consists of a component comprising an area that receives the seal and made of a material that is less prone to extruding than the seal material, which is typically made from a non-metallic elastic material.
Some of the supporting components currently used comprise a portion generally extending below the heel and part of the sealing lip of the seal body. Due to demanding service conditions associated with dynamic applications where such supporting components may be used, they are to be made of a relatively high elastic modulus material, such as steel. At the same time, such demanding service conditions require a reduced extrusion gap, which may result in the inner surface of the referred portion of the supporting component touching the shaft due to excessive deflection under media pressure. However, a relatively high elastic modulus material may catastrophically damage the shaft if it touches the shaft due to deflection, vibration, or any other reason.